The outer foreskin layer is a continuation of the skin of the shaft of the penis.
The inner foreskin layer is not just "skin," but mucocutaneous tissue of a unique type found nowhere else on the body.
The ridged band is the interface (join) between the outer and inner foreskin layers. When the penis is not erect, it tightens to narrow the foreskin opening. During erection, the ridged band forms ridges that go all the way around, about halfway down the shaft.
The reddish or purplish glans or glans penis (head of the penis) is smooth, shiny, moist and extremely sensitive.
The frenulum, or frenum, is a connecting membrane on the underside of the penis, similar to that beneath the tongue.